Vehicle with air conditioning system

ABSTRACT

A vehicle includes an air conditioning system for conditioning intake air flowing into a vehicle interior. The air conditioning system has a primary heat exchanger in thermal communication with a drive unit via a coolant circuit, a compressor, and a secondary heat exchanger which is disposed jointly with the compressor in a refrigerant circuit. The secondary heat exchanger operates as a condenser in a heating mode of the air conditioning system and jointly with the primary heat exchanger gives off heat to the intake air. A control device controls operation of the refrigerant circuit in response to an input by a user. The control device includes an evaluation unit to carry out a comparison between a desired heat supply commensurate with the input by the user and a determined actual heat supply, and generates an output signal for operating the compressor in response to the comparison.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of German Patent Application, Serial No. 10 2010 054 957.6, filed Dec. 17, 2010, pursuant to 35 U.S.C. 119(a)-(d), the content of which is incorporated herein by reference in its entirety as if fully set forth herein.

BACKGROUND OF THE INVENTION

The present invention relates to a vehicle with air conditioning system, and to a method of operating an air conditioning system.

The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.

The vehicle interior is heated as inflowing air is warmed up using a heat exchanger to which waste heat from an internal combustion engine for example is conducted via a coolant circuit. As the amount of generated waste heat is generally slight in modern vehicles, an auxiliary heater is typically associated to the heat exchanger in order to compensate the difference to a required total heating output. An example of an auxiliary heater includes a PTC (Positive Temperature Coefficient) heating element.

It would be desirable and advantageous to provide an improved vehicle with air conditioning system and an improved method of operating an air conditioning system to obviate prior art shortcomings.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a vehicle includes an air conditioning system for conditioning intake air flowing into a vehicle interior, with the air conditioning system having a primary heat exchanger in thermal communication with a drive unit via a coolant circuit, a compressor, a secondary heat exchanger disposed jointly with the compressor in a refrigerant circuit, the secondary heat exchanger operating as a condenser in a heating mode of the air conditioning system and jointly with the primary heat exchanger giving off heat to the intake air, and a control device controlling operation of the refrigerant circuit in response to an input by a user, the control device including an evaluation unit to carry out a comparison between a desired heat supply commensurate with the input by the user and a determined actual heat supply, and generating an output signal for operating the compressor in response to the comparison.

According to another advantageous feature of the present invention, the actual heat supply can be determined only on the basis of a parameter of the intake air. As a result, there is no need for executing complex measurement of parameters of the coolant circuit or refrigerant circuit.

According to another advantageous feature of the present invention, the compressor has a maximum output that can be set by the control device and is at a level to allow the secondary heat exchanger to generate a heat output which exceeds a heat output of a conventional PTC (Positive Temperature Coefficient) heating element. In contrast to a PTC heating element, the provision of the secondary heat exchanger in accordance with the present invention allows a significantly greater efficiency, i.e. the primary energy that has to be used is significantly less compared to a conventional auxiliary heating concept. As the maximally adjustable output of the compressor enables a greater heating output than conventional auxiliary heating concepts such as conventional PTC heating elements, the risk for “oversized” concepts when using the coolant circuit as heat pumps is reduced. In general the output data is directly proportional to the energy consumption. The present invention allows application of a control concept which ensures the operation of the heat pump at a defined output limit beforehand.

According to another advantageous feature of the present invention, the actual heat supply can be ascertained by using temperature sensors which respectively detect an air entry temperature and an air exit temperature of the heating assembly comprised of the primary and secondary heat exchangers. The temperature sensors may be arranged downstream and upstream of the heating assembly, respectively.

According to another advantageous feature of the present invention, a determination unit may be operatively connected to the evaluation unit and adapted to determine an air mass flow of the intake air for ascertaining the actual heat supply. The determination of the air mass flow of the intake air can be carried out by special measuring elements. Currently preferred is however an indirect determination of the air mass flow of the intake air on the basis of operating parameters of already installed equipments. For example, in the presence of a special ventilation structure in the flow path of the intake air, a flow flap and a fan may be provided for transport of the air mass flow of the intake air, with the flow flap and the fan being placed upstream of the heating assembly to allow adjustment of a flow cross section and flow rate of the intake air.

According to another advantageous feature of the present invention, the determination unit can be constructed to determine the air mass flow as a function of an electric fan output of the fan or a fan parameter in correlation with the electric fan output, and a flap position of the flow flap. Depending on the flap position, the flow flap is able to adjust the air mass flow of the intake air through the heating assembly or a bypass air mass which circumvents the heating assembly.

In such a configuration, the determination unit is able to determine the air mass flow of the intake air on the basis of an electric fan output and flap position of the flow flap. For this purpose, the determination unit can store a characteristic diagram from which the resultant air mass flow can be read out when inputting a value pair comprised of fan output and flap position. The characteristic diagram can be defined empirically on the basis of experiments.

According to another advantageous feature of the present invention, the air conditioning system may include an air conditioner arranged upstream of the heating assembly and including an evaporator which is disposed in the refrigerant circuit. When operating in the heating mode, the coolant circuit components can be controlled in such a way that the evaporator is idle while only the secondary heat exchanger operates as condenser. In the cooling mode, on the other hand, the secondary heat exchanger is idle while the evaporator is adapted to absorb heat from the intake air.

According to another advantageous feature of the present invention, the air conditioning system can have a temperature sensor which is operably connected to the evaporator for ascertaining an evaporation temperature in the cooling mode. The temperature sensor can advantageously be provided on the outside of the evaporator. To reduce the number of components, the evaporator-side temperature sensor can be so constructed to assume a dual function involving not only detection of the evaporation temperature but in addition also the air entry temperature of the heating assembly in the heating mode.

According to another aspect of the present invention, a method of operating an air conditioning system of a vehicle includes determining an actual heat supply into a vehicle interior, comparing the determined actual heat supply with a desired heat supply commensurate with a user's input, generating a manipulated variable as a function of the comparison, and operating a compressor in response to the output signal and causing a secondary heat exchanger to operate as a condenser in a heating mode of the air conditioning system so as to give off heat to the intake air flowing into the vehicle interior air jointly with a primary heat exchanger, when the actual heat supply is below the desired heat supply.

BRIEF DESCRIPTION OF THE DRAWING

Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:

FIG. 1 is a circuit diagram of an air conditioning system of a vehicle, operating in the heating mode; and

FIG. 2 is a circuit diagram of the air conditioning system of FIG. 1, operating in the cooling mode.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.

Turning now to the drawing, and in particular to FIG. 1, there is shown a circuit diagram of an air conditioning system of a vehicle for cooling or heating a vehicle interior 2 of a vehicle, not shown in greater detail. FIG. 1 shows the air conditioning system operating in the heating mode to heat the vehicle interior 2. Those components of the air conditioning system through which coolant flows are highlighted by thicker lines in comparison to those components that are idle when operating the air conditioning system in the heating mode. Accordingly, coolant is routed from a compressor 3 via a 3/2 directional control valve 5 to a first high-pressure conduit 6 which leads in the direction of the arrow to an auxiliary or secondary heat exchanger 7. The secondary heat exchanger 7 is arranged within an air channel in an air conditioner 9, indicated by dashed line, with intake air I being conducted by the air channel to the vehicle interior 2.

The secondary heat exchanger 7 forms jointly with a primary heat exchanger 8 a heating assembly 10 through which the intake air I flows. The primary heat exchanger 8 is arranged in a coolant circuit 13 which is only hinted here by a dash-dot line and used to conduct waste heat generated by an internal combustion engine (not shown) to the primary heat exchanger 8.

According to FIG. 1, the secondary heat exchanger 7 operates as condenser which is in flow communication with a radiator-side heat exchanger 17 via a second high-pressure conduit 11 and a 3/2 directional control valve 12 with interposition of an expansion valve 15. The radiator-side heat exchanger 17 operates in the heating mode as an evaporator which draws heat from ambient air. The radiator-side heat exchanger 17 is connected downstream via a low-pressure conduit 19 to the intake side of the compressor 3. The low-pressure conduit 19 is routed via an internal heat exchanger 21 in which a heat exchange can take place to the high-pressure side, i.e. to the high-pressure conduit 11.

As further shown in FIG. 1, the air conditioner 9 is in flow communication with an upstream air channel portion 31 in which a fan 33 is arranged for conveying the intake air I. Disposed downstream of the fan 33 is a branch point by which the air channel 31 is split into a bypass line 34 and a feed line 35, with the feed line 35 conducting intake air I to the air conditioner 9. Arranged in the branch point is a temperature mixing flap 36 which adjusts the flow cross section in the feed line 35 in dependence on the flap position.

A control device 37 is provided for control of the refrigerant circuit of the air conditioning system based on a user's input. For that purpose, the control device 37 generates an output signal Y for operating the compressor 3. The output signal Y is generated by the control device 37 in response to a determination of intake parameters by temperature sensors 39, 40 which are provided in the air conditioner 9 and arranged upstream and downstream of the heating assembly 10, respectively. The temperature sensors 39, 40 ascertain the air entry temperature T_(e) and the air exit temperature T_(a) of the heating assembly 10. In addition, as shown in FIG. 1, a position sensor 41 is provided to detect the actual angle position W of the flow flap 36 and to transmit a respective signal to a determination unit comprised of program modules 42, 43.

In addition to the angle position W of the flow flap 36, the electric voltage U_(G) of the fan 33 is also ascertained. The electric voltage U_(G) correlates with the fan output and a respective signal is transmitted to the determination unit 42, 43. The program module 42 of the determination unit stores a characteristic diagram from which the actual air mass flow of the intake air I can be read out in response to an input of an angle position W and a fan voltage U_(G). A communication link is provided between the program module 42 and the program module 43, with the program module 43 ascertaining the actual heat supply Q_(actual) on the basis of a temperature difference between the air entry temperature T_(e) and the air exit temperature T_(a) and on the basis of the ascertained air mass flow m. The determined actual heat supply Q_(actual) can be compared in an evaluation unit 38 of the control device 37 with a desired heat supply Q_(desired) as inputted by a user. As a result of this comparison, the control device 37 generates the output signal Y for operating the compressor 3.

Compared to a conventional PTC heating element, the secondary heat exchanger 7 allows realization of a far superior heating output through respective operation of the compressor 3. This affords the user a greater comfort level. Also, the comfort in the vehicle interior 2 can be maintained by simply regulating down the compressor 3 to a predefined output limit.

FIG. 2 shows the operation of the air conditioning system in the cooling mode, with the conduits through which coolant flows being highlighted by thick lines. In the cooling mode, the 3/2 directional control valve 5 blocks downstream of the compressor 3 the high-pressure conduit 6 which leads to the secondary heat exchanger 7 in the air conditioner 9 whereas an intermediate conduit 23 opens to the low-pressure conduit 19. A shut-off valve 25 is arranged at a branch point to the conduit 19 at a side distal to the heat exchanger 17 and assumes a closed switching position. As a result, coolant is able to flow through the radiator-side heat exchanger 17 which operates as condenser in the cooling mode to give off heat to the ambient air.

The coolant then flows via a one-way valve 27 placed parallel to the expansion valve 15, via the internal heat exchanger 21, and via the 3/2/directional control valve 12, to an evaporator 29 disposed within the air conditioner 9. Disposed upstream of the evaporator 29 is an expansion valve 32. The control of the coolant circuit in the cooling mode may be realized with the aid of the control device 37 in like manner as in the heating mode. The difference to FIG. 1 resides in the fact that in the cooling mode as shown in FIG. 2, the actual heat flow to be removed from the intake air I can be determined on the basis of a temperature difference between an evaporator entry temperature and an evaporator exit temperature. The evaporator entry temperature is hereby detected by a temperature sensor 45 while the evaporator exit temperature is detected by the temperature sensor 40.

While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein: 

1. A vehicle, comprising an air conditioning system for conditioning intake air flowing into a vehicle interior, said air conditioning system comprising: a primary heat exchanger in thermal communication with a drive unit via a coolant circuit, a compressor, a secondary heat exchanger disposed jointly with the compressor in a refrigerant circuit, said secondary heat exchanger operating as a condenser in a heating mode of the air conditioning system and jointly with the primary heat exchanger giving off heat to the intake air, and a control device controlling operation of the refrigerant circuit in response to an input by a user, said control device including an evaluation unit to carry out a comparison between a desired heat supply commensurate with the input by the user and a determined actual heat supply, and generating an output signal for operating the compressor in response to the comparison.
 2. The vehicle of claim 1, wherein the compressor has a maximum output that can be set by the control device and is at a level to allow the secondary heat exchanger to generate a heat output which exceeds a heat output of a conventional PTC (Positive Temperature Coefficient) heating element.
 3. The vehicle of claim 1, wherein the actual heat supply is determined only on the basis of a parameter of the intake air.
 4. The vehicle of claim 1, wherein the primary and secondary heat exchangers form a heating assembly, further comprising temperature sensors constructed to ascertain an air entry temperature and an air exit temperature of the heating assembly, respectively, to thereby determine the actual heat supply.
 5. The vehicle of claim 3, further comprising a determination unit operatively connected to the evaluation unit and adapted to determine an air mass flow of the intake air for ascertaining the actual heat supply.
 6. The vehicle of claim 5, wherein the primary and secondary heat exchangers form a heating assembly, and further comprising a flow flap and a fan for transport of the air mass flow of the intake air, said flow flap and said fan being placed upstream of the heating assembly to allow adjustment of a flow cross section and flow rate of the intake air.
 7. The vehicle of claim 6, wherein the determination unit is constructed to determine the air mass flow as a function of an electric fan output of the fan or a fan parameter in correlation with the electric fan output, and a flap position of the flow flap.
 8. The vehicle of claim 1, wherein the primary and secondary heat exchangers form a heating assembly, said air conditioning system including an air conditioner arranged upstream of the heating assembly and including an evaporator which is disposed jointly with the secondary heat exchanger in the refrigerant circuit, said evaporator being idle in the heating mode and adapted to absorb heat from the intake air in a cooling mode of the air conditioning system while the secondary heat exchanger is idle.
 9. The vehicle of claim 8, wherein the air conditioning system has a temperature sensor operably connected to the evaporator for ascertaining an evaporation temperature in the cooling mode, said temperature sensor adapted to ascertain an air entry temperature of the heating assembly in the heating mode.
 10. The vehicle of claim 9, wherein the temperature sensor is arranged on an outside of the evaporator.
 11. A method of operating an air conditioning system of a vehicle, comprising: determining an actual heat supply into a vehicle interior; comparing the determined actual heat supply with a desired heat supply commensurate with a user's input; generating an output signal as a function of the comparison; and operating a compressor in response to the output signal and causing a secondary heat exchanger to operate as a condenser in a heating mode of the air conditioning system so as to give off heat to the intake air flowing into the vehicle interior air jointly with a primary heat exchanger, when the actual heat supply is below the desired heat supply.
 12. The method of claim 11, wherein the compressor has a maximum output that can be set by the control device and is at a level to allow the secondary heat exchanger to generate a heat output which exceeds a heat output of a conventional PTC (Positive Temperature Coefficient) heating element.
 13. The method of claim 11, wherein the actual heat supply is determined only on the basis of a parameter of the intake air.
 14. The method of claim 11, wherein the determining step includes detecting an air entry temperature and an air exit temperature of a heating assembly comprised of the primary and secondary heat exchangers.
 15. The method of claim 13, wherein the parameter is an air mass flow of the intake air.
 16. The method of claim 15, further comprising controlling a transport of the air mass flow of the intake air by adjusting a flow cross section and a flow rate of the intake air.
 17. The method of claim 16, wherein the air mass flow is determined as a function of an electric fan output of a fan or a fan parameter in correlation with the electric fan output, and a flap position of a flow flap upstream of a heating assembly comprised of the primary and secondary heat exchangers.
 18. The method of claim 11, further comprising operating an evaporator to absorb heat from the intake air in a cooling mode of the air conditioning system while idling the secondary heat exchanger.
 19. The method of claim 11, further comprising idling the evaporator in the heating mode of the air conditioning system.
 20. The method of claim 18, further comprising ascertaining an evaporation temperature in the cooling mode by a temperature sensor, and ascertaining in the heating mode an air entry temperature of a heating assembly comprised of the primary and secondary heat exchangers, using the temperature sensor. 